The television industry has been striving to improve the quality of displayed television images. Several techniques which have been employed using standard broadcast television signals include adaptive luma/chroma separation using line and frame comb filters such as described in U.S. Pat. No. 4,617,589, adaptive recursive filters such as described in U.S. Pat. No. 4,639,784, and adaptive non interlaced or progressive scan display scanning apparatus such as described in U.S. Pat. No. 4,598,309. Each of these systems have the potential to significantly improve the displayed images, however the potential has not been fully realized. Each of the systems in general provide the anticipated potential improvements for sequences of particular images. On the other hand for image sequences including, for example, motion of objects within successive images or camera panning, image quality suffers due to the failure to implement cost competitive error free parameter detectors used to control the adaptive processing.
More ambitious techniques to improve image quality involve changes to the standard broadcast signal by adding signal components which among other things effectively increase the luminance signal bandwidth while maintaining the overall signal compatible for reception by current "standard" receivers. Special or extended definition television (EDTV) receivers have been developed to receive the altered broadcast signals and utilize the added signals to produce images of remarkable quality. A difficulty exists in these systems in including sufficient information in the allotted channel spectrum space while maintaining backward compatibility of the signal. An example of an extended definition system is described by M. A. Isnardi et al. entitled "Decoding Issues In The ACTV System", IEEE Trans. on Consumer Electronics, Vol. 34, No. 1, February 1988, pp. 111-120 (also described in U.S. patent application Ser. No. 139,340 filed Dec. 29, 1987). In the Isnardi et al. system three additional signal components are added to the standard NTSC broadcast signal. These signals are amplitude and/or bandwidth compressed before addition to the NTSC signal to avoid their causing interference/artifacts in standard receivers. One of the added components called the V-T helper signal contains interframe difference information which is used by the EDTV receiver to convert the interlaced broadcast video signal into non-interlaced display signals. Due to the amplitude compression of this signal, in noisy environments, the helper signal may fail to provide adequate information.